00:00 Dark matter is an invisible glue that holds everything together, but we don't know what it is.

04:19 Astronomers have discovered that the amount of visible matter in the universe is too small to account for the mass of galaxies and galaxy clusters, leading to the hypothesis of the existence of dark matter, an invisible and mysterious form of matter that does not emit or absorb light.

09:13 Dark matter is a term used to describe the unaccounted for mass in the universe that cannot be detected and is either an undiscovered particle or a misunderstanding of physics.

13:50 Two different ways of measuring the mass and gravity of remote bodies in the universe don't align, indicating that there is something missing and yet to be discovered that is accounting for this discrepancy.

18:41 Astrophysicists are using advanced computer models to map dark matter in the universe, even though dark matter itself cannot be directly observed.

23:37 Astrophysicists have used data from Chandra's X-ray Observatory and the Canada, France, Hawaii telescope to create real maps of dark matter, which have confirmed the accuracy of computer models.

28:17 The big question is whether dark matter is just existing matter that we can't observe yet, or if it is some new matter that we haven't discovered, or if our understanding of physics is wrong; one proposal is that dark matter is made up of massive structures that we already know about but can't see clearly, while another idea is that dark matter is made up of hypothetical particles called WIMPs that interact weakly with ordinary matter and are difficult to detect because they don't interact with the electromagnetic force.

32:51 Dark matter could potentially be made up of particles that interact with the strong nuclear force rather than the electromagnetic force, and some astronomers have proposed alternative theories to Newton's laws of motion to explain dark matter.

37:27 The density of matter in the universe determines whether the universe will continue to expand forever or eventually reach a "heat death."

41:32 The only way to determine the fate of the universe is to figure out how much matter there is, including dark matter, in order to predict whether it will continue to expand or eventually reach a state of heat death.